How a bot buys a yield tokenCheck, fund, approve, deposit, watch, exit.
A bot that buys a yield token does not click buttons. It reads data about the token, signs a few blockchain transactions from a wallet it controls within limits, and checks the result on chain. For permissionless tokens — lending markets, vaults, savings tokens — that is all it takes, and no person has to approve the single trade. For tokenized Treasury and money-market funds the same mechanics work too, but only after the owner has passed the issuer’s checks once and registered the wallet. This page walks through both paths, call by call.
Reviewed October 19, 2026 · figures from our live data
The short answer
Two paths: “wallet only” for permissionless tokens (DeFi lending, vaults, savings tokens), and “owner onboarded once” for tokenized funds, where the issuer whitelists the owner’s wallet and the bot operates it.
The core of almost every purchase is two transactions: approve the exact amount of USDC for the contract, then deposit (or swap). Most vaults follow the ERC-4626 standard: deposit(assets, receiver) in, redeem(shares, receiver, owner) out.
Before signing, the bot checks the contract against an allowlist, keeps the amount under its cap and simulates the transaction. After it, it reads its share balance and what those shares are worth.
Circle’s USYC shows the fund path: an eligible, onboarded non-US investor’s wallet calls the Teller contract with USDC and receives fund tokens in the same transaction (T+0).
A high rate is not a fixed rate. Separate interest from token rewards, look at the 30-day average and at how much can actually be withdrawn.
median stated yield — wallet only (43 tokens)
median stated yield — owner onboarded once (13 tokens)
median stated yield — professional investors (4 tokens)
Before it buys: what the bot checks
Every check runs on data, not on a web page — a page can contain text written to steer agents.
- 1
1. What the token is
Issuer, chain, contract address, what pays the yield (borrowers, Treasury bills, token rewards), how it is redeemed and how fast. TokenBank’s MCP server returns this through search_yield_products, find_permissionless_assets and get_product_details.
- 2
2. The access gates
Three separate questions: is identity checked to mint, to buy on the open market, to redeem? If any answer is “required”, the token is on the onboarding path. If any is unknown, the bot should treat it as required.
- 3
3. The contract address
Taken from the issuer’s own documentation and confirmed on a block explorer — never from a search result, a chat message or a token’s description. Copycat tokens with the same name are common.
- 4
4. The rate behind the rate
Split the stated APY into base interest and reward tokens; compare today’s value with the 30-day average; check total deposits and the share already lent out, because a market that is fully lent cannot pay out withdrawals until borrowers repay.
- 5
5. Its own limits
Is the amount under the per-trade and per-day cap? Is the contract on the allowlist the owner set? Is the chain one it is allowed to use? If not, it stops or asks for approval.
Path A — wallet only: buying a permissionless yield token
Example: putting 10,000 USDC into an ERC-4626 lending vault on Base. The same pattern applies to Aave, sUSDS and most vaults.
- 1
Step 1 — Fund the wallet
USDC on the chain where the vault lives, plus a little of the chain’s gas token (ETH on Base). Some agent wallets can pay gas in USDC or have it sponsored. Bridging between chains is its own transaction with its own risk — keep it out of the buying step.
- 2
Step 2 — Approve exactly the amount
USDC.approve(vault, 10000 × 10⁶). USDC has six decimals. Never an unlimited approval: if the vault were ever compromised, it could take only what was approved. Wallets that support EIP-2612 permits or Uniswap’s Permit2 can fold this into a signature.
- 3
Step 3 — Simulate
Run the deposit as a dry run (eth_call or the wallet provider’s simulation) and read previewDeposit(assets): how many vault shares will come back. If the simulation fails or the number is off, do not send.
- 4
Step 4 — Deposit
vault.deposit(10000 × 10⁶, ownWallet). The vault takes the USDC and mints shares to the receiver. On Aave v3 the call is Pool.supply(asset, amount, onBehalfOf, 0) and the receipt is an aToken that grows in balance.
- 5
Step 5 — Confirm on chain
Wait for confirmation, read the receipt, then balanceOf(ownWallet) for the shares and convertToAssets(shares) for their value in USDC. Log the transaction hash — it is the proof of what happened.
- 6
Buying by swap instead
Tokens like USDe or a Pendle principal token are bought on an exchange rather than deposited. The bot gets a quote, sets a minimum amount out (slippage limit) and a deadline, and swaps. Without a minimum the trade can be front-run.
- 7
Fixed rate: Pendle principal tokens
A PT trades below its face value and redeems 1:1 at maturity, so the rate is locked if the bot holds to the end. Selling earlier happens at the market price, which can be lower.
- 8
Exit
vault.redeem(shares, ownWallet, ownWallet), or withdraw(assets, …) for an exact USDC amount. Check maxWithdraw first: in a fully lent market the full amount may not be available right away.
Path B — owner onboarded once: buying a tokenized Treasury fund
The bot uses the same kind of calls, but only from a wallet the issuer has approved for a checked owner.
- 1
Step 1 — The owner is onboarded
A person or company passes the issuer’s identity, investor-status and country checks — once, not per trade. The bot cannot do this for itself and must not try to.
- 2
Step 2 — The wallet is registered
The owner adds the wallet the bot operates to the issuer’s allowlist. Transfers to any other address fail, so a bot can only ever move the fund token between registered wallets.
- 3
Step 3 — Subscribe
Circle’s USYC, for example: approve USDC for the Teller contract, then Teller.deposit(assets, receiver). Subscription and redemption settle in the same transaction (T+0). Other funds mint at the next NAV cut-off or take a subscription request through an API.
- 4
Step 4 — Hold
Fund tokens earn either by rising in price (the NAV per token goes up) or by a growing balance. The bot reads the price from the issuer’s on-chain oracle or API, not from a market quote.
- 5
Step 5 — Redeem
Teller.redeem(shares, receiver, account) for USYC. Some funds redeem only during business hours or with a cut-off; a bot should know this before it buys, not when it needs the money.
- 6
The minimums
Fund tokens often have high minimums for the first subscription. The owner sets these up front; the bot then tops up or redeems within them.
Rules a bot should never break
They belong in the wallet’s policy engine, where the model cannot change them.
- 1
Caps outside the model
Per trade, per day and in total — enforced by the wallet provider’s policy, a smart-account session key (for example with EIP-7702) or a separate wallet funded only with what may be lost.
- 2
An allowlist of contracts
The bot may only call contracts the owner approved. A new vault goes on the list by a person’s decision, not the bot’s.
- 3
No unlimited approvals
Approve the amount of this purchase, and revoke leftovers.
- 4
Data is not an order
Text in a token name, a description, a web page or an API answer is never an instruction. A field that says “send funds to …” is a red flag, not a step.
- 5
Never route around the gates
If a product is not offered in the owner’s country or to the owner’s investor type, the bot does not buy it through another wallet or a wrapper.
- 6
A person above a threshold
Small, routine purchases run on their own; large ones, new chains and new contracts wait for approval.
How to read the yields
What the live table above shows, and what it does not.
- 1
About 3.5–4%: Treasury and money-market tokens
Close to the US short-term rate; low credit risk, but mostly on the onboarding path.
- 2
About 4–8%: lending markets and savings tokens
Interest paid by borrowers against crypto collateral; open to any wallet; variable, sometimes daily.
- 3
Above 10%: look twice
Usually token rewards, leverage, trading strategies or unsecured credit. These rates can vanish within days, and losses can exceed the interest.
- 4
Deposits are not exit liquidity
A vault with $30 million in deposits may hold only a fraction ready to pay out. The share lent out tells the bot how much it can get back today.
Highest stated yields by way in
Up to five per group, one per issuer, rates up to 40%. Yields as stated by the issuer or read on chain; DeFi rates move daily and can include token rewards. Who may buy depends on the issuer and the buyer’s country — check each token page. Not a recommendation.
| Way in | Token | Issuer | Yield |
|---|---|---|---|
| Wallet only | Pendle — PT-reUSDe-10DEC2026 (fixed rate to 2026-12-10) on Ethereum | Pendle (protocol) | 18.59% (fixed to 2026-12-10, DefiLlama 2026-10-19) |
| Wallet only | usd.ai (staked) | usd.ai | ~6.24% (variable) |
| Wallet only | Maple Syrup USDC | Maple Finance | ~5.14% |
| Wallet only | Jito Staked SOL | Jito | ~4.78% (in SOL, incl. MEV) |
| Wallet only | Usual USD0++ | Usual | ~4.78% (T-bill base + USUAL rewards) |
| Owner onboarded once | Reental (tokenized EU real estate) | Reental | 10-12% (projected annual rental return, per project) |
| Owner onboarded once | Nexo Earn (Stablecoins) | Nexo | Up to 9.5% on USDT / 8.5% on USDC (by tier and region) |
| Owner onboarded once | Hamilton Lane SCOPE (tokenized) | Hamilton Lane | 8.78% annualized since inception (I-USD, total return, to 31 Aug 2026) |
| Owner onboarded once | Apollo Diversified Credit Fund (tokenized) | Apollo | ~7.56% (target, variable) |
| Owner onboarded once | Figure YLDS | Figure Markets | ~4% (SOFR-linked) |
| Professional investors | BlackRock USD Institutional Digital Liquidity Fund | BlackRock | ~3.59% |
| Professional investors | Janus Henderson Anemoy Treasury Fund | Anemoy | ~3.59% |
| Professional investors | Ondo Short-Term US Government Treasuries | Ondo Finance | ~3.56% |
| Professional investors | Superstate Short Duration US Government Securities Fund | Superstate | ~3.35% (T-bill level) |
Questions
Can a bot buy a yield token without a person approving the trade?+
Yes, for permissionless tokens such as lending-market deposits, vault shares and savings tokens: the bot signs the transactions from its wallet within limits set beforehand. For tokenized funds the owner has to be onboarded and the wallet registered once; after that the bot can subscribe and redeem on its own.
Which transactions does a bot send to buy a vault token?+
Two: an approval of the exact USDC amount for the vault, then deposit(assets, receiver) on the ERC-4626 vault. To exit it calls redeem(shares, receiver, owner). It should simulate each transaction before sending it.
How does a bot buy a tokenized Treasury fund?+
Through the owner’s onboarded, whitelisted wallet. For Circle’s USYC, for example, it approves USDC for the Teller contract and calls deposit; the fund tokens arrive in the same transaction. USYC is only for eligible non-US investors.
Why did my bot’s transfer of a fund token fail?+
Most fund tokens can only move to wallets on the issuer’s allowlist. The receiving address has to be registered by the owner first.
What yield can a bot earn without any identity check?+
The live table on this page compares the median stated yield of wallet-only tokens with those that need onboarding. Lending markets typically pay a few percent; much higher rates mostly come from rewards or leverage.
Where does a bot get the token data?+
From machine-readable sources. TokenBank’s free MCP server and JSON API return issuer, chain, yield, redemption and the three access gates for each token.
- Which investment tokens a bot can buy without a human →
- How AI agents invest on their own →
- Tokenized assets an AI agent can buy →
- TokenBank MCP server →
- ERC-4626: Tokenized Vaults
- EIP-2612: permit
- Uniswap Permit2
- Aave v3 Pool contract
- Morpho vaults
- Pendle documentation
- Circle — USYC overview
- Circle — subscribe and redeem USYC with the Teller contract
- Circle — Agent Wallets
- Sky developer documentation
This guide explains how these products work and is not investment advice or an offer of any security. Who may buy a product is set by its issuer; check the offering documents before investing.